1. Field of the Invention
This invention pertains method and apparatus for receiving optical signals used to determine vehicle velocity, and particularly to method and apparatus for receiving laser signals used to determine the velocity of a vehicle.
2. Prior Art and Other Considerations
For decades radar techniques have been utilized to determine the velocity of a vehicle. According to conventional radar techniques, a high frequency (e.g., microwave) carrier wave is directed toward a travelling target vehicle for a period of time. Return energy reflected from the target vehicle is processed to obtain an indication of the velocity of the vehicle.
The widespread use of radar for highway and traffic surveillance has encouraged many motorists to install radar receiver devices (also known as radar detectors) in their vehicles. However, the advent of optical surveillance techniques for traffic speed enforcement has rendered obsolete most radar detection devices. For example, in recent years laser velocity detection devices have been introduced which employ a series of invisible laser light pulses.
One type of such laser velocity detection device is known as Lidar (Light Detection and Ranging), which measure both the range and velocity of vehicular targets. These laser velocity detection devices broadcast a relatively narrow beam which can be more discriminately aimed at a moving vehicle. For the most part, the light pulses broadcast by the laser devices are not detectable by the receivers of conventional radar detection devices.
Therefore, it is an object of the present invention to provide method and apparatus for receiving optical signals used to determine vehicle velocity.
An advantage of the present invention is the provision of method and apparatus for detecting whether optical traffic surveillance techniques are being employed.
Another advantage of the present invention is the provision of an optical receiving method and apparatus operable in conjunction with conventional radar detector devices.
A further advantage of the present invention is the provision of method and apparatus providing an indication of the directionality of the source of traffic surveillance optical signals.
Another advantage of the present invention is the provision of method and apparatus providing multi-field coverage.
Yet another advantage of the present invention is the provision of method and apparatus which accommodates a plurality of ranges of optical wavelengths in detecting whether optical traffic surveillance techniques are being employed.